1. Technical Field
This invention relates to a creasing device for creasing paper or card before it is folded.
2 . Background
A high percentage of printed stock such as book covers or greetings cards needs to be creased before the next operation of folding can be carried out.
Existing methods of creasing involve feeding the paper to be creased between an upper drum and a pair of lower drums. A metal disc is affixed to the upper drum and projects a short distance radially outwards around the circumference of the upper drum. The two lower drums are mounted coaxially and are spaced apart a short distance to create a narrow gap between them. The disc projecting from the upper drum is received in the gap between the two lower drums. When the upper and lower drums are counter-rotated and paper is fed between them, the projecting disc forces the paper into the gap, deforming it into the desired crease.
This method has the disadvantage that mounting of the metal disc on the upper drum is slow. Obtaining the correct spacing between the two lower drums and aligning it correctly with the disc is critical to the success of the operation and is a skilled operation. Also, the metal disc can damage the paper, particularly causing it to tear at the edges.
A very small percentage of printers will have in-house facilities to tackle the creasing operation. Most medium sized printers, for example, will regularly send such work out to be processed at a specialized print finishers.
Even so, a high degree of this work is then cut to size on a guillotine and then processed for a second time through a folding machine (common to most printers). Although the carrying out of these operations are priced into the job, accordingly, the long drawn out system can often cause a delay in its delivery to the customer and an increase in costs.
The invention is a creasing device consisting or a drum-shaped male component featuring grooves of variable widths and depths to hold rubber O-rings or inserts. The female component is almost identical to the male component, apart from the grooves being slightly wider and deeper. When fixed to the top and bottom shafts of the unit with one O-ring or insert on the male component aligned with a groove of the female component, a sheet of paper fed between them will be creased by the pressure of the O-ring or insert forcing the paper into the groove.
According to the present invention the specialized processes described in the xe2x80x9cBackgroundxe2x80x9d can be eliminated. The first unit of a commonly used folding machine can be adapted to mount the male and female components to operate the creasing method. By using different O-rings or inserts and/or different grooves on the male component, the device can quickly and easily be adapted to form different widths and depths of creases in different thicknesses of paper. The grooves in the female component are automatically aligned with the corresponding O-rings or inserts in the male component.
The rubber O-rings or inserts treat the paper more gently and are less likely to tear it than the metal discs of the prior art. Hardened rubber or a similar resilient material is chosen to avoid wear. Once worn, the rings can be quickly and easily replaced.